The present disclosure relates to improved biocatalysts and improved biocatalytic processes for the preparation of the active pharmaceutical ingredient, (1-(4-fluorophenyl)-3(R)-[3-(4-fluorophenyl)-3(S)-hydroxypropyl]-4(S)-(4-hydroxyphenyl)-2-azetidinone) (shown below as compound (1)) and derivatives and analogs thereof.

Compound (1) is commonly known as Ezetimibe and is the active ingredient in ZETIA®, manufactured by Merck/Schering-Plough Pharmaceuticals. Ezetimibe has been approved by the United States Food and Drug Administration for use in patients with high cholesterol to reduce LDL cholesterol and total cholesterol (see e.g., U.S. Pat. No. 6,207,822). Ezetimibe lowers high levels of blood cholesterol by selectively inhibiting the intestinal absorption of cholesterol and related phytosterols. Ezetimibe is commercially available in combination with simvastatin in the VYTORIN™ formulation from MSP Pharmaceuticals, Inc.
Numerous compounds that are analogs of Ezetimibe and being developed as possible therapeutics for lowering cholesterol are also known in the art (see e.g., PCT publications WO2006/17257A2, WO 2008/085300A1, and WO2008/039829A2).
Synthetic processes for the production of Ezetimibe and Ezetimibe derivatives have been previously disclosed. A variety of publications have disclosed chemical synthesis using a late reduction scheme that delays the reduction of the alcohol to the carbonyl to the last step of the reaction: U.S. Pat. Nos. 5,886,171, 5,738,321, WO 2005/0066120, WO 2007/030721, WO 2007/120824, WO 2007/119106, WO 2007/072088, WO 2007/030721, and WO 2007/120824.
U.S. Pat. No. 6,133,001 and WO 2000/060107 disclose using certain microorganisms (e.g., Rhodococcus fascians ATCC No. 202210 or Geotrichum candidum ATCC No. 74487) to carry out the stereoselective reduction of 1-(4-fluorophenyl)-3(R)-[3-oxo-3-(4-fluorophenyl)propyl)]-4(S)-(4-hydroxyphenyl)-2-azetidinone to 1-(4-fluorophenyl)-3(R)-[3(S)-hydroxy-3-(4-fluorophenyl)-propyl)]-4(S)-(4-hydroxyphenyl)-2-azetidinone. This is a microbial process, however, carried out under whole cell fermentation conditions.
WO 2008/151324A1 discloses using certain commercially available ketoreductase biocatalysts to prepare Ezetimibe and protected Ezetimibe analogs from the corresponding precursor ketone compounds. The biocatalysts and processes disclosed therein, however, use low substrate loadings (25 g/L or less), a GDH/glucose cofactor regeneration system, and result in low percentage conversion of substrate to the Ezetimibe product (˜65% yield).
US20100062499A1 discloses engineered ketoreductase enzymes, and methods of using the engineered ketoreductase enzymes to convert the diketone compound, 5-(4S)-2-oxo-4-phenyl(1,3-oxazolidin-3-yl))-1-(4-fluorophenyl)pentane-1,-5-dione, to the chiral alcohol, (4S)-3-[(5S)-5-(4-fluorophenyl)-5-hydroxypentanoyl]-4-phenyl-1,3-oxazolid- in-2-one. This chiral alcohol made biocatalytically is an early stage intermediate that can be used in a process for making Ezetimibe.
It is desirable to have improved biocatalysts and a biocatalytic process having increased efficiency for use in a late stage biocatalytic reduction scheme for preparing Ezetimibe in high diastereomeric excess (>98% d.e.). Particularly desirable would be engineered biocatalysts capable of increased activity in large scale processes having high substrate loadings (e.g., >50 g/L), high percent conversion (e.g., >90% in 24 h), without the need for an additional cofactor regenerating enzyme, and capable of yielding Ezetimibe as product in high purity and diastereomeric excess.